In order to decrease cutting time and thereby increase production, industry, under present state of the art, is using materials such as Silicon Nitride and Cubic Boron Nitride that will permit boring of cast iron at rates in excess of 3,000 feet per minute. Problems presented by this are: (1) the materials (SiNi and CBN) are expensive and the high machining rates also require high spindle speeds, frequently in excess of 4,000 R.P.M. This can cause premature spindle bearing wear.
Face milling tools are known in the art with incremental cutting insert positions such as the FACE MILLING CUTTER disclosed in U.S. Pat. No. 4,586,855 wherein it is an important feature that the axial steps between successive inserts be very small, preferably less than about 0.01" with steps in the range of 0.002 to 0.005" being preferred with cast iron or steel workpieces. In a typical face mill illustrated in such patent, ten equally spaced inserts were axially stepped by a distance of 0.002 and radially stepped by an amount of 0.090". Each chip removed at a thickness of 0.002" and length of 0.640" and radial step in on the part of 0.026". The total depth of cut between the workpiece finished face and the top surface of the material to be removed was 0.020".